An error occurred while synchronizing edits

[BerhanuMekonen]

I tested the offline data collection-Collector for ArcGIS using a future hosted on AGOL, it works well but,  a big but,   am challenged in synchronizing, it move up to 50% and then fail with error massage -
"An error occurred while synchronizing edits"  
Would you please help?

[JanicePeal]

I have found the answer to my sync issue and thanks everyone for your input.  Turns out, the inability to sync was due to an issue with our IIS 7 web server and arcgis web adaptor settings.  In IIS, if you go to your web adaptor name, then the WebAdaptor folder, check out the UploadReadAheadSize setting.  The default value was 41942, and ESRI told me to up it to 20 million.  This solved the issue! 

[RobertRayner1]

Funny, I went through a similar situation of chasing bugs and re-publishing different services last year which was finally resolved with the same solution Janice.

Hopefully people find these posts and save time, seems like it should be an earlier troubleshooting step in the ESRI ArcGIS Collector handbook! 

Below is the step by step solution:

These are the instructions that ESRI provided on changing the uploadreadaheadsize:

1. Launch “Internet Information Services (IIS) Manager”
2. Select the site that you are hosting your web application under it.
3. In the Features section, double click “Configuration Editor”
4. Under “Section” select: system.webServer ,then select serverRuntime
5. 5. Modify the “uploadReadAheadSize” section to be like 20MB (the value there is in Bytes)
6. 6. Click Apply this is happening as during renegotiation step;

Hopefully this helps others!

And this is the similar thread: Offline works in ios but not android

[GideonDalrymple]

I've increased mine to 500mb and still came back with the same error. I have like 66 new edits with about 40 attachments. Could the number of attachments be the issue? All are photos. 

[GideonDalrymple]

Also is there a way to also copy the attachments along with the database so that they also can be appended? 

[HeatherStanton]

I just wanted to add that changing the uploadReadAheadSize worked for us, too.

[Kylie]

Gideon Dalrymple‌ Could you please start a new question so that we can best help you? This thread is rather old.